For decades, scientists have been puzzled by a puzzling phenomenon: the moon, despite having no inherent magnetic field today, holds rocks infused with powerful magnetism.
Now, a new study from MIT researchers proposes a groundbreaking explanation: ancient lunar impacts, not just a global dynamo, might have significantly shaped the moon’s magnetic anomalies.
The team suggests that when a massive asteroid struck the moon, it carved out a colossal basin and generated a plasma cloud, charged particles that interacted with the moon’s weak magnetic field.
The result? A temporary surge in magnetism is strong enough to imprint itself onto lunar rocks, particularly those near the moon’s south pole.
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Their simulations reveal that as the plasma enveloped the moon, it concentrated on the opposite side of the impact, potentially explaining why some of the most magnetized lunar rocks lie on the far side, near the south pole.
Interestingly, this location directly aligns with the Imbrium basin’s near-side position, suggesting the impact that formed Imbrium may have triggered this magnetic phenomenon.
While past theories pinned lunar magnetism on a weak dynamo generated by the moon’s core, this new research introduces an alternative mechanism combining impact-driven plasma flow with seismic shocks that “reset” rock magnetization in a brief, intense window of time. The team estimates this amplified magnetic state lasted for just 40 minutes, but that was enough to leave a lasting imprint.
“This process could explain much of the moon’s surface magnetism observed today,” says lead author Isaac Narrett of MIT’s Department of Earth, Atmospheric and Planetary Sciences.
Large-scale meteorite impacts may have formed ancient rocks on the Moon
The discovery offers an exciting avenue for future exploration. With Artemis missions set to investigate the lunar south pole, scientists may soon test this hypothesis by analyzing the region’s magnetized rocks.
Could impacts have played a bigger role in shaping planetary magnetism than previously thought? This study opens the door for new investigations into how collisions influence celestial bodies—not just the moon but perhaps even Mars and ancient Earth.
Journal Reference:
- Issac Narrett, Rona Oran, Yuxi Chen et al. Impact plasma amplification of the ancient lunar dynamo. Science Advances. DOI: 10.1126/sciadv.adr7401
